Extend lexers.Get() to support filenames.

Fixes #94.

lexers/api.go

@@ -3,6 +3,7 @@ package lexers
 import (
 	"path/filepath"
 	"sort"
+	"strings"
 
 	"github.com/danwakefield/fnmatch"
 
@@ -33,12 +34,34 @@ func Names(withAliases bool) []string {
 	return out
 }
 
-// Get a Lexer by name.
+// Get a Lexer by name, alias or file extension.
 func Get(name string) chroma.Lexer {
+	candidates := chroma.PrioritisedLexers{}
 	if lexer := Registry.byName[name]; lexer != nil {
-		return lexer
+		candidates = append(candidates, lexer)
 	}
-	return Registry.byAlias[name]
+	if lexer := Registry.byAlias[name]; lexer != nil {
+		candidates = append(candidates, lexer)
+	}
+	if lexer := Registry.byName[strings.ToLower(name)]; lexer != nil {
+		candidates = append(candidates, lexer)
+	}
+	if lexer := Registry.byAlias[strings.ToLower(name)]; lexer != nil {
+		candidates = append(candidates, lexer)
+	}
+	// Try file extension.
+	if lexer := Match("filename." + name); lexer != nil {
+		candidates = append(candidates, lexer)
+	}
+	// Try exact filename.
+	if lexer := Match(name); lexer != nil {
+		candidates = append(candidates, lexer)
+	}
+	if len(candidates) == 0 {
+		return nil
+	}
+	sort.Sort(candidates)
+	return candidates[0]
 }
 
 // MatchMimeType attempts to find a lexer for the given MIME type.
@@ -112,8 +135,10 @@ func Analyse(text string) chroma.Lexer {
 func Register(lexer chroma.Lexer) chroma.Lexer {
 	config := lexer.Config()
 	Registry.byName[config.Name] = lexer
+	Registry.byName[strings.ToLower(config.Name)] = lexer
 	for _, alias := range config.Aliases {
 		Registry.byAlias[alias] = lexer
+		Registry.byAlias[strings.ToLower(alias)] = lexer
 	}
 	Registry.Lexers = append(Registry.Lexers, lexer)
 	return lexer

lexers/api_test.go

@@ -19,3 +19,15 @@ func TestCompileAllRegexes(t *testing.T) {
 		assert.NoError(t, err, "%s failed", lexer.Config().Name)
 	}
 }
+
+func TestGet(t *testing.T) {
+	t.Run("ByName", func(t *testing.T) {
+		assert.Equal(t, lexers.Get("xml"), lexers.XML)
+	})
+	t.Run("ByAlias", func(t *testing.T) {
+		assert.Equal(t, lexers.Get("as"), lexers.Actionscript)
+	})
+	t.Run("ViaFilename", func(t *testing.T) {
+		assert.Equal(t, lexers.Get("svg"), lexers.XML)
+	})
+}